The present invention relates to tubular bodies formed with a longitudinally extending adhesively-bonded lap side seam and more particularly is concerned with the construction of the adhesively-bonded lap side seam.
In the formation of a lap side seam, the overlapped marginal edges usually terminate in a raw metal edge. The outer surface of the tubular body may be readily protected against various forms of chemical attack by the application over this surface, including the raw metal edge on the outside lap, of some sort of protective coatings.
However, it has been found to be exceedingly difficult to adequately protect and cover the raw metal edge on the inside lap by means heretofore known to the prior art. This is the case, for example, where the tubular body is a container in which it is desired to package a particularly corrosive substance, such as a carbonated beverage.
Accordingly, the present invention is concerned with a novel construction of the adhesively-bonded lap side seam wherein the inside lap has a crease running the entire length of the body blank, which crease is imbedded into the side seam adhesive on the opposite surface of the outside lap.
The purpose, therefore, for creasing or bending the inside lap edge portion of the body blank is so that during the subsequent tubular body forming operations the raw metal edge on the inside lap will be more easily and effectively buried and covered with the side seam adhesive and, further, the side seam stripe and topcoat.
The advantage or benefit to be gained by covering the raw metal edge on the inside lap is the protection of the raw metal edge from chemical attack by a corrosive substance within the tubular body. Particularly, with regard to containers for packaging carbonated beverages, the advantage in burying the raw metal edge on the inside lap into the side seam adhesive is in the substantial reduction of iron pickup by a corrosive carbonated beverage which will ultimately be packaged within the container.
Even though the present invention has particular importance with regard to tubular bodies used as containers for carbonated beverages, the invention also has been found useful in connection with other uses for lap side seam tubular bodies, such as telephone cables, where certain materials within the cable may chemically attack any exposed raw metal surfaces inside the cable.